/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.instrument.classloading.glassfish;

import java.lang.instrument.ClassFileTransformer;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.springframework.core.OverridingClassLoader;
import org.springframework.instrument.classloading.LoadTimeWeaver;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * {@link LoadTimeWeaver} implementation for GlassFish's
 * {@code org.glassfish.api.deployment.InstrumentableClassLoader InstrumentableClassLoader}.
 *
 * <p>As of Spring Framework 5.0, this weaver supports GlassFish 4+.
 *
 * @author Costin Leau
 * @author Juergen Hoeller
 * @since 2.0.1
 */
public class GlassFishLoadTimeWeaver implements LoadTimeWeaver {

    private static final String INSTRUMENTABLE_LOADER_CLASS_NAME =
            "org.glassfish.api.deployment.InstrumentableClassLoader";


    private final ClassLoader classLoader;

    private final Method addTransformerMethod;

    private final Method copyMethod;


    /**
     * Create a new instance of the {@link GlassFishLoadTimeWeaver} class using
     * the default {@link ClassLoader class loader}.
     *
     * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
     */
    public GlassFishLoadTimeWeaver() {
        this(ClassUtils.getDefaultClassLoader());
    }

    /**
     * Create a new instance of the {@link GlassFishLoadTimeWeaver} class using
     * the supplied {@link ClassLoader}.
     *
     * @param classLoader the {@code ClassLoader} to delegate to for weaving
     */
    public GlassFishLoadTimeWeaver(@Nullable ClassLoader classLoader) {
        Assert.notNull(classLoader, "ClassLoader must not be null");

        Class<?> instrumentableLoaderClass;
        try {
            instrumentableLoaderClass = classLoader.loadClass(INSTRUMENTABLE_LOADER_CLASS_NAME);
            this.addTransformerMethod = instrumentableLoaderClass.getMethod("addTransformer", ClassFileTransformer.class);
            this.copyMethod = instrumentableLoaderClass.getMethod("copy");
        } catch (Throwable ex) {
            throw new IllegalStateException(
                    "Could not initialize GlassFishLoadTimeWeaver because GlassFish API classes are not available", ex);
        }

        ClassLoader clazzLoader = null;
        // Detect transformation-aware ClassLoader by traversing the hierarchy
        // (as in GlassFish, Spring can be loaded by the WebappClassLoader).
        for (ClassLoader cl = classLoader; cl != null && clazzLoader == null; cl = cl.getParent()) {
            if (instrumentableLoaderClass.isInstance(cl)) {
                clazzLoader = cl;
            }
        }

        if (clazzLoader == null) {
            throw new IllegalArgumentException(classLoader + " and its parents are not suitable ClassLoaders: A [" +
                    instrumentableLoaderClass.getName() + "] implementation is required.");
        }

        this.classLoader = clazzLoader;
    }


    @Override
    public void addTransformer(ClassFileTransformer transformer) {
        try {
            this.addTransformerMethod.invoke(this.classLoader, transformer);
        } catch (InvocationTargetException ex) {
            throw new IllegalStateException("GlassFish addTransformer method threw exception", ex.getCause());
        } catch (Throwable ex) {
            throw new IllegalStateException("Could not invoke GlassFish addTransformer method", ex);
        }
    }

    @Override
    public ClassLoader getInstrumentableClassLoader() {
        return this.classLoader;
    }

    @Override
    public ClassLoader getThrowawayClassLoader() {
        try {
            return new OverridingClassLoader(this.classLoader, (ClassLoader) this.copyMethod.invoke(this.classLoader));
        } catch (InvocationTargetException ex) {
            throw new IllegalStateException("GlassFish copy method threw exception", ex.getCause());
        } catch (Throwable ex) {
            throw new IllegalStateException("Could not invoke GlassFish copy method", ex);
        }
    }

}
